Tuberculous
bronchopneumonia presents radiologically as multiple, often bilateral,
patchy, "cotton-wool" densities. These occur when tubercle
bacilli are forced or inhaled into multiple terminal bronchial segments
during coughing, either when an open pulmonary lesion (cavity) communicates
with a bronchus, or when an infected lymph node has ruptured into a
bronchus (Fig. 5.8). In nontropical countries, this radiological
pattern of bronchopneumonia usually suggests staphylococcal infection
and the acute clinical presentation in the tropics may be very similar.
The tuberculous patient, usually a young child or baby but sometimes
an adult or elderly person, can be severely ill clinically. The sputum
invariably contains many tubercle bacilli, but the tuberculin skin test
is often negative, especially in the early stages or when the patient
is HIV-positive.

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Fig. 5.8 A-F. Complications of primary tuberculosis:
the progressive primary infection. A An African infant from Kenya
with bilateral bronchopneumonia and lymphadenopathy due to acute primary
tuberculosis. B Bilateral "fluffy" bronchopneumonia
in a young Indian adult. In the right lung some of the consolidation
is cavitating. Clinically this was an acute illness resembling staphylococcal
pneumonia, but the sputum contained many M. tuberculosis. C,
D This adult had a 24-hour history of cough, sputum, headache, and
feeling unwell. There is bilateral bronchopneumonia and hilar lymphadenopathy.
The lateral view shows well-marked calcification in the paratracheal
lymph nodes. There were many M. tuberculosis in the sputum. The
response to antituberculous therapy was clinically dramatic, but much
slower radiologically. Presumably this was a primary infection, unknown
to the patient and healing satisfactorily as shown by the nodal calcification.
One of the lymph nodes had ruptured into a bronchus and caused the acute
bilateral inhalation bronchopneumonia and his acute illness. E
This child was being treated for primary tuberculosis and improving
clinically. After 3 months treatment, she suffered an acute upper respiratory
infection and became acutely ill, with a high temperature, severe cough,
and obvious ill health. There is resolving right upper lobe pneumonia
and enlarged right hilar and paratracheal lymph nodes complicated later
(F) by bronchogenic spread throughout both lungs with fluffy
ill-defined aleoar infiltrites and multiple thin-walled cavities (abscesses).
(C-E courtesy of Semin Roentgenol, 1979).

Radiologically
the infection is usually bilateral and widespread, but not always symmetrical.
There may be multiple thin-walled cavities (lung abscesses), together
with the fluffy ill-defined densities (Fig. 5.8F). The appearances
change daily, and the thin-walled cavities may vary in size, be empty
or contain fluid, expand, and develop a surrounding pulmonary reaction.
This sequence depends not only on the severity of the infection and
the resistance of the patient, but also on the accumulation of secretion
in the cavity and how frequently and how well it is coughed out. In
progressive primary tuberculous infections there will be marked bilateral
adenopathy in almost every patient, the nodes being large and ill defined.
(When a similar bronchogenic spread occurs during the secondary, or
immune stage of tuberculosis, there is no adenopathy.) In this acute
bronchopneumonic, cavitating pattern of tuberculosis, any of the peripheral
tuberculous lung abscesses may rupture into the pleura or pericardium,
resulting in a tuberculous empyema or pericarditis.

Histological
examination at this stage shows that the lungs contain multiple thin-walled
abscesses which are filled with caseous pus. This can be demonstrated
by CT, particularly with high resolution and thin sections. It must
be differentiated from bronchiectasis by the finding of relatively normal
bronchi and the absence of atelectasis.

Calcification
in this pattern of infection is uncommon, in either the lung foci or
in the nodes. In some patients infection is so acute that it may cause
death: if the patient recovers, the end result can be a remarkably normal
chest radiograph or one showing only a little scarring.

The differential
diagnosis includes staphylococcal pneumonia. Adenopathy is extremely
rare in similar cavitating pyogenic infections, most of which are the
result of septicemia with a visible source of infection, such as osteomyelitis
or an infected skin ulcer. In both tuberculous and staphylococcal infections
there can be hepatosplenomegaly.